Dopaminergic control of neonatal salt and water metabolism

There is reason to believe that the dopaminergic system plays a role in the control of salt and water metabolism in the neonate. Therefore, we performed a series of studies designed to test this assumption and reveal the relationship between dopamine (DA) and other factors known to affect salt and water balance. The postnatal course of urinary dopamine excretion was assessed in a group of premature infants kept on low or high salt diet. A clear association between sodium depletion and increased DA excretion, and between reduction in DA excretion and restoration of salt balance was demonstrated. In premature infants with cardiopulmonary distress, DA therapy resulted in an increase in sodium and water diuresis, enhanced plasma renin activity (PRA) and decreased plasma prolactin level; the plasma aldosterone (pAldo) level remained stable. Metoclopramide (MTC), a specific DA antagonist given to premature infants to treat functional gastrointestinal disturbances, induced an increase in Na+ and water excretion which was associated with significant falls in plasma and urinary aldosterone, but left PRA unaltered. Arginine vasopressin excretion also fell after MTC, but this change was not associated with increased free water clearance. These results suggest that endogenous DA has no apparent influence on PRA and, contrary to findings in adults, it stimulates the secretion of aldosterone and vasopressin and thus tubular sodium and water reabsorption.